Western Digital Blue Ultraslim WD5000MPCK 500GB 5400RPM (5mm) 16MB Cache (SFF-8784 SATA Express) 6.0Gb/s 2.5" Hard Drive 500GB Capacity, 5400RPM Rotation Speed, 16MB Cache 3.5" Internal Hard Drive, SFF-8784 (SATA Express) Interface 5MM Height 2.5" Hard Drive, For Ultrabook laptop or Tablet (Microsoft Surface) NOTE: It is NOT a SATA interface 2.5" hard drive, it will NOT fit regular SATA laptop without conversation kit or cable.